1. Field of the invention
This invention relates to a magnetic head having a magnetic path formed by a magnetic metal film, and a manufacturing method therefor.
2. Description of Related Art
In a magnetic recording/reproducing apparatus, such as a video tape recorder, researches in digitizing signals and recording the resulting digitized signals for improving the picture quality, are under way. In keeping pace therewith, researches in increasing the recording density and the recording frequency, are also progressing.
Meanwhile, with the increased magnetic recording density and increased recording frequency, a magnetic head loaded on the magnetic recording/reproducing apparatus is required to have a high output and a low noise in the high frequency range. For example, in a compound metal-in-gap magnetic head used frequently as a magnetic head for VTR, in which a magnetic metal film is formed on a ferrite material and a coil is placed thereon, has a large inductance and a low output per inductance, as a result of which the output is low in the high frequency range. Thus, it is difficult to cope sufficiently with digital picture recording for which a high frequency and a high density are required.
Under these circumstances, a so-called thin film type magnetic head, fabricated by the thin film forming step, is being investigated as a magnetic head for coping with the high frequency.
This thin film type magnetic head is formed by connecting a pair of magnetic head halves having magnetic metal films via a gap material in-between. In the magnetic head halves is embedded a magnetic metal film having its connecting surface formed by a non-magnetic material, such as glass, and substantially rectangular-shaped coil-forming recesses are formed at mid portions thereof. In the coil-forming recesses of the magnetic head halves is placed a coil formed by a thin film forming technique, such as photolithography. These magnetic head halves are joined together via a non-magnetic gap material in-between for forming the magnetic gap between the magnetic metal films.
With the above-described thin-film type magnetic head, it has been difficult to form the magnetic metal films in position for facing each other on a sole substrate. That is, in the above-described magnetic head, one of the thin magnetic metal films becomes offset relative to the other film, as shown in FIG. 1. The magnetic head shown in FIG. 1 undergoes so-called track offset, with an offset angle being .theta.. In the present magnetic head, an azimuth angle is represented by .alpha..
In the above-described magnetic head, an angle defined between the counter-azimuth direction shown by arrow R in FIG. 1 and the bisector of the angle of track offset shown at Q in FIG. 1 becomes small. The result is that, in the conventional magnetic head, neighboring recording tracks are reproduced, thus producing the noise. That is, this magnetic head suffers from high playback fringing.
With the present magnetic head, it may be premeditated that, as shown in FIG. 2, one of the thin magnetic metal films 100 be relatively offset to the other metal film in an opposite direction to that shown in FIG. 1. With this magnetic head, the angle.times. between the opposite azimuth direction R and the bisector Q of the angle of track offset in this case becomes larger thus suppressing the playback fringing to a smaller value. However, in the magnetic head shown in FIG. 2, the track offset angle .theta. is of a smaller value.
In a magnetic head, the larger the angle of track offset .theta., the smaller is the recording fringing value. That is, in the present magnetic head, if the track offset angle .theta. is small, signals are recorded on the neighboring recording track, thus partially erasing the signals of the neighboring track. Thus, if the thin magnetic metal films 100 are relatively offset, as shown in FIG. 25, the recording fringing is of a higher value, because the track offset angle .theta. is small.
The above-mentioned defects in the recording/reproducing characteristics due to relative position offset of the magnetic thin film 100 can be evaded by setting the magnetic thin metal films in position relative to each other. That is, in the conventional magnetic head, the track offset angle .theta. can be set so as to be as large as 90.degree. or more by bonding the paired magnetic metal films in position for facing each other. This renders it possible to suppress the recording fringing and the reproducing fringing to a lower value thus achieving optimum recording/reproducing characteristics.
However, it is extremely difficult to bond the paired magnetic metal films in position for facing each other. For correctly positioning the paired thin magnetic metal films in position, the manufacturing device needs to be improved in accuracy significantly, which is not a realistic method for solution. It may also be premeditated to remove track offset by laser trimming after bonding the paired magnetic thin metal films. In this case, laser trimming is applied to each magnetic head in the manufacturing process of simultaneously fabricating plural magnetic heads, thus not only complicating the manufacturing process but also requiring excess working time.